The present invention relates to a transport mechanism. More specifically, the present invention relates to a transferred mechanism adaptable for different terrains and to pass over various obstacles. Such a transport mechanism is useful in a large variety of vehicles. In the following, the term xe2x80x9cvehiclexe2x80x9d will be used to denote any mobile device making use of wheels or close tracks for transport including cars, trucks, hand trucks, wheelchairs, vehicles dedicated for specific applications, etc.
A very wide variety of transport mechanisms are known. On the one extreme are wheels, which are characterized by a minimal contact with the ground, and hence minimal friction or drag develops with the surface over which the vehicle tracks, and on the other extreme are chains and belts which contact the ground over a relatively large surface, and hence have a large drag. Wheels are adapted for transport over essentially solid surfaces, whereas chains are intended far use on rough or loose ground terrains, such as soil or snow, or for overcoming different obstacles.
The transport mechanism of a vehicle is designed according to the terrain or the type of surface for which the vehicle is intended. However, at times, the vehicle is confronted with terrains different than that to which it is designed, or has to overcome various obstacles. For example, field vehicles which are at times provided with regular, air field rubber wheels, have an installation allowing deflating of the wheels in order to increase surface grip, e.g. when passing in an area with loose or muddy ground.
Wheelchairs are typically provided with a wheel, which is either hand or motor-powered, which allows safe transport of handicapped individuals over flat and hard surfaces. However, there is a serious problem in transporting a wheelchair over various obstacles, e.g. such as the edge of a sideboard, stairs, etc., as well as to transport a wheelchair over unpaved ground or snow.
It is the object of the invention to provide a novel transport mechanism which is versatile in that it can be configured to transfer a vehicle, such as a wheelchair, over different terrains, to allow it to safely pass over various obstacles, etc.
The present invention provides a transport mechanism for transporting a load-bearing assembly, said transport mechanism comprising:
a closed flexible track supported at an internal side thereof by at least two support rollers, which at a first position one of the support rollers exerts a force having a downward component on to the flexible track at a point of contact thereof with a ground surface;
biasing arrangement for biasing said flexible track so as to assume a substantially circular shape; and
a displacing mechanism couple to at lest one of said support rollers for manually displacing the support roller into a second position, against said basing arrangement, in which the support rollers force the track to assume a state in which an extended portion thereof is in contact with the ground surface and at least two of said support rollers are positioned at two ends of said portion.
In accordance with one embodiment of the invention, the transport mechanism is motor operated, in accordance with this embodiment at least one of the support rollers are coupled to a motor and the flexible track is engaged with said at least one support rolling for imparting rotary motion to said track.
In accordance with one preferred embodiment of the invention, the transport mechanism is a transport mechanism of a wheelchair.
The load-bearing assembly may be, for example, a setting unit of a wheelchair, a platform in a hand truck, a body of a vehicle, etc.
It should however be noted that the invention is not limited to this embodiment, as will also be illustrated further below.
In accordance with a embodiment of the invention, said flexible track is made of a resilient material with stiff and springy reinforcement wire embedded therein for biasing the flexible track to assume its essentially circular shape.
In accordance with another embodiment, the flexible track is made of a resilient material with stiff radial projections from the internal side of the flexible track, each of the projections being connected to adjacent projections by resilient linking elements for biasing the flexible track to assume its substantially circular shape. A track in accordance with this embodiment may be made of a continuous flexible body, or alternatively, may consist of a plurality of segments pivotally connected to one another.
In accordance with still another embodiment, a first of the at least two support rollers is mounted at an end of a first arm, and a second of the at least two support rollers is mounted at an end of a second arm displaceable with respect to the first arm. At a first state of the mechanism the first and the second support rollers are positioned at opposite ends of a line defining the diameter of the circular shape; at a second state the first and second support rollers are positioned such that they are in contact with the track at portions thereof which contact the ground.
The load-bearing assembly may be connected directly to one or more of the support rollers. Alternatively, the load-bearing assembly is connected to the displacing mechanism of the transport assembly. In the latter case, the load-bearing assembly may be associated with a mechanism for angular displacement of the load-bearing assembly with respect to the displacing mechanism responsive to position and inclination of the flexible track so as to retain a stable center of gravity.
In accordance with one embodiment of the invention, the load-bearing assembly is associated with a mechanism for maintaining it at an essentially horizontal position, regardless of the position and inclination of the flexible track.
In accordance with still a further embodiment of the invention, the flexible track consists of two sets of identical links, each link having a first and a second face, a first and second radial edge, a peripheral edge forming part of the track""s periphery and an internal edge; the links of each set being arranged in a closed path with the first radial edge of each link facing and being adjacent the second radial edge of an adjacent link, and with the first faces of links of one set facing the first faces of links of the other set; each link of one set being pivotally linked at a first corner thereof defined by the first radial edge and by the peripheral edge with the first corner of one link of the second set, and pivotally linked at a second corner thereof, defined by the second radial edge and by the internal edge with the second corner of a link of the other set adjacent said one link; there being a biasing member biasing each link to converge with respect to the adjacent links.
In accordance with another embodiment, the flexible track consists of a plurality of identical segments connected to one another by links; each segment having a peripheral edge forming part of the track""s periphery, an internal edge and two side edges, the side edges being inclined such that when the track assumes its circular shape, side edges of adjacent segments are in contact with one another; the segment being connected to the links at corners formed between the peripheral and side edges in a slidable and pivotal manner; the track further comprising one or more biasing members biasing segments towards one another. Such biasing members may be a resilient strap or a non-resilient strap which is manually tensioned to apply the biasing force on the segments for assuming the circular shape of the track.
According to still another embodiment of the present invention one of the support rollers is mounted on a first arced rail and another of the support rollers is mounted on a second arced rail co-axial with the first arced rail, said arced rails being mutually slidably displaceable with respect to one another so as to displace the respective support rollers between the first and second positions.
By a further aspect the present invention also provides a track for use in the above transport mechanisms with specifications as defined.
The invention will now be illustrated in a non-limiting manner in the following specific embodiments with reference to the annexed drawings: